Protect the trigger action of pan control by checking whether

we were added to a map prior to calling this.map.pan().

lib/OpenLayers/Control/Pan.js

@@ -70,7 +70,7 @@ OpenLayers.Control.Pan = OpenLayers.Class(OpenLayers.Control, {
      * Method: trigger
      */
     trigger: function(){
-    
+        if (this.map) {
             var getSlideFactor = OpenLayers.Function.bind(function (dim) {
                 return this.slideRatio ?
                     this.map.getSize()[dim] * this.slideRatio :
@@ -91,6 +91,7 @@ OpenLayers.Control.Pan = OpenLayers.Class(OpenLayers.Control, {
                     this.map.pan(getSlideFactor("w"), 0);
                     break;
             }   
+        }
     },
 
     CLASS_NAME: "OpenLayers.Control.Pan"